We will keep the main.cpp, sum_integers.cpp, and sum_integers.hpp unchanged from the previous recipe, but will update the test.cpp:

#include "sum_integers.hpp"
  
// this tells catch to provide a main()
// only do this in one cpp file
#define CATCH_CONFIG_MAIN
#include "catch.hpp"

#include <vector>

TEST_CASE("Sum of integers for a short vector", "[short]") {
  auto integers = {1, 2, 3, 4, 5};
  REQUIRE(sum_integers(integers) == 15);
}

TEST_CASE("Sum of integers for a longer vector", "[long]") {
  std::vector<int> integers;
  for (int i = 1; i < 1001; ++i) {
    integers.push_back(i);
  }
  REQUIRE(sum_integers(integers) == 500500);
}

We also need the catch.hpp header, which we can download from https://github.com/catchorg/Catch2 (we have used version 2.0.1) and place in the root of our project, alongside test.cpp.